Do I Need a High Speed (Large Maximum Aperture) Lens?

Canon 24-105 RF f/4 L

Canon 24-105 RF f/4 L

Hey folks! An excellent question came in a little bit ago. The individual was moving from a DSLR to a mirrorless camera and was planning on going with some new glass built for the new mount.

The question was arising from making the decision about the first RF lens. The person wanted to stay with Canon brand lenses and expected that this first lens would be the one used most often. There are a lot of options that could fit the necessary use cases.

  • 24-70 RF f/2.8 L $2399

  • 28-70 RF f/2 L $3099

  • 24-105 RF f/4 L $1099

The individual has been using the EF 24-70/2.8L as the go to lens for some time and was pleased with Canon L series glass and wanted to stay in the L family.

As we can see from these USD B&H prices, the optically faster lenses are not inexpensive. If we anticipate at least 6 years use of any lens, you can do a return on usage annual number which appeals to financial folks.

The more important question noted that as lens speed increases, focal length range decreases, so the decision to just buy faster doesn’t hold because lens flexibility changes.

Now I am an old guy who started photographing before there were high quality zooms. I remember the release of the old Nikkor 43-86 which was, IMO, the first zoom lens of excellent optical quality albeit with limited range and relatively slow lens speed.

My general guidance on fast lenses is to only buy them IF you are going to shoot them wide open the majority of the time. When I was shooting film in the 35mm format, I had a 50mm f/1.2 which cost a lot more than the very common and very sharp f/1.7 or even the f/1.4 available at the time. That lens worked in very low light allowing me to use lower ISO films in poor light and to deliver the razor thin depth of field that f/1.2 allowed for.

When I went digital, I still wanted lens speed, less for ISO issues because digital noise is only really apparent if the photo is lousy and boring (IMO) and I don’t pixel peep, but because I wanted that razor thin depth of field and with a bit more reach, so my first fixed focal length lens (aka prime) was an 85mm f/1.2 I always wanted a 200mm f/2 but never had enough business with the need of that lens, so never got it.

The point is that with the 85mm I shoot it wide open most of the time. If I were using it mostly at f/2.8 or smaller, that would be an indicator that I made a purchase mistake because I would have spent a lot of money for functionality I was not using.

Working with the questioner, we used the EXIF data stored in the Lightroom database to determine the highest frequency aperture used on the EF 24-70 which has a maximum aperture of f/2.8 What the data told us is that the photographer shot mostly at f/5.6 and smaller,, so the premium for f/2 or f/2.8 did not make sense. We also learned that the focal lengths in use most often were 24mm and 70mm. This suggested that focal length agility was very important.

This led to the purchase decision to go with the 24-105 RF f/4L which saved enough money to allow the photographer to also get the 70-200 RF f/4L for only $200 more than would have been paid for the 24-70 RF f/2.8L A better buy that better fit the actual needs of the photographer. Also smaller and lighter, a tangible bonus.


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